CLARIFICATION: Law enforcement officials say they do not have evidence to support a claim by the leader of a white supremacist militia in Florida that Parkland high school shooter Nikolas Cruz trained with the group. Friday’s editorial about the massacre included the group’s claim.

It is time for energy and action, not hopelessness and cynicism.

The failure to respond to past mass shootings in a way that prevented even more is no excuse to stop trying, or to keep failing. There is plenty we can do to stop or lessen future Parkland, Las Vegas or Newtown-type massacres. Claiming otherwise shirks our moral responsibility, and surrenders to carnage in a battle for the lives of our children and the soul of our nation.

Nikolas Cruz, 19, returned Wednesday to the high school that expelled him in Broward County, Florida. He fatally shot 17 students and faculty and wounded 15 more. As the violence erupted, TV screens showed children and teachers fleeing the school. Teenagers potentially facing death posted wrenching messages on social media.

What we know about Cruz and his path to this violent day is frightening and enlightening. His story illustrates both society’s failure to stop such violence and the changes we can make to prevent such killings.

Cruz was reportedly violent and scary. He talked about his guns, and posed with them on social media. A white nationalist group says he was a member and participated in paramilitary drills. He suffered from mental health issues and sought treatment. His adoptive parents died. He bought an AR-15 semi-automatic rifle, high-capacity magazines and loads of ammunition.

So, knowing all this and all we’ve learned from other mass killings, how do we make the nation safer, while acknowledging that law-abiding Americans do have the properly regulated right to own certain guns?

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We do what the vast majority of Americans support, what the National Rifle Association fights and what President Donald Trump did not deign to mention in his address to the nation Thursday.

We change this culture to stop identifying big, fierce weapons and violence as components of a toxic heroic masculinity and toughness. Women don’t commit these random killings, but they die in them and lose their children to them. Men such as Cruz who glorify weapons and violence are cowards and ought to be clearly treated as such.

We outlaw the purchase and possession of weapons meant only for lightning-fast murder, and ban huge caches of ammunition and magazines intended for no other purpose than to attack those who are defenseless.

We monitor who buys guns and make it harder for those plotting violence to do so. We demand that gun owners be vetted and trained and even licensed and insured, and that securing and locking their weapons become clear legal responsibilities.

We increase security at schools and other vulnerable facilities.

We improve mental health care.

We guard as much against potential domestic mass killers born here who hide behind white supremacy as we do against potential mass killers from foreign countries who act in the name of radical Islam.

We vote out elected officials who won’t fight for these safeguards.

This country did begin to change after Columbine, and then after Virginia Tech, Sandy Hook and Las Vegas. It just never finished changing our laws and our culture and our willingness to accept these killings.